Conversion of hydrocarbon oils and gases



June 27, 1939. W, E, KUHN 2,164,293

CONVERSION OF HYDROCARBON OILS AND GASES Filed MaICh 13, 1957 WAYNE E. KUHN INVE TOR BY (Noam-:Y

Patented June 27, 1939 UNITED STATES CONVERSION OF HYDROCARBON OILS AND GASES Wayne E. Kuhn, Port Arthur, Tex., assignor to The Texas Company, New York, N. Y., a corporation of Delaware Application March 13,

2 Claims.

This invention relates to the conversion of hydrocarbon oils and gases and has to do particularly with a combination gas polymerization and oil cracking process in which the gases intended for polymerization are contacted with a hydrocarbon oil to absorb a portion of the gases to aid in the oil cracking process and the mixture of oil and absorbed gases subjected to cracking.

More particularly, according to the invention, a hydrocarbon gas, such as natural or refinery gases, preferably after stabilization, is scrubbed with a suitable cracking stock such as gas oil, crude residuum, heavy naphtha and the like, to absorb a portion of the gases in the cracking stock and the mixture of cracking stock and ab sorbed hydrocarbon gases is thensubjected to cracking conditions of temperature and pressure. The scrubbed gases unabsorbed in the oil may then be subjected to thermal polymerization. The cracking of the mixture of hydrocarbon oil and absorbed gases is intended to involve the principles of gas reversion whereby a larger yield of improved motor fuel products is obtained.

The invention is particularly applicable to the treatment of a refinery gas containing a substantial amount of unsaturated hydrocarbons, whereby the scrubbing operation functions to concentrate or selectively extract the oleflns in the hydrocarbon oil.. The presence of the olens in the cracking stock is particularly advantageous, whereby the yield of motor fuel is appreciably increased and formation of undesirable products, such as coke and tars, is decreased. It has been found in this type of operation that the recycle stock from a cracking operation may advantageously be used for the scrubbing of the hydrocarbon gas.

The invention will be more fully understood from the following description taken in connection with the accompanying drawing showing a diagrammatic sketch of one form of apparatus for practicing the invention.

Referring to the drawing, a gas charge which may be natural or refinery gas, or a mixture thereof, is introduced from a suitable source of supply, not shown, through the line l and forced by the pump 2 through the line 3 to a fracti-onator or stabilizer 5. According to the process c-ontem* plated by the drawing, the gases are largely in the liquid phase and it is intended that fractionation take place in the stabilizer whereby fixed gases, such as C1 and C2 hydrocarbons, are largely separated and withdrawn from the top of the stabilizer through the line 6. It is to be understood, however, that the hydrocarbons may be 1937, Serial N0. 130,620

mainly in the gaseous phase, in which case the stabilizer 5 may be omitted. The particular type of operation will depend upon the pressures maintained. Under pressures of about pounds or less the hydrocarbons will be largely in a gaseous phase, Whereas if a presssure of about 40G-600' pounds or above is used, the hydrocarbons will be largely in the liquid phase. The fractionated product, usually consisting predominantly of C3 and C4 hydrocarbons, is Withdrawn from the bottom of the stabilizer 5 through the line 'l and forced by the pump 3 through the line 9 to an absorber Ill. In this absorber the gases pass countercurrent to a scrubbing oil which may be a cracking stock introduced through the line I2 and forced by the pump I3 wholly or in part through the line lll to the top of the scrubber. In case all of the oil is not charged to the absorber, the remainder may be passed through the line i5 directly to the cracking coil I6, referred to hereinafter. In the absorber l 0, a substantial amount of the gaseous hydrocarbons is absorbed in the scrubbing oil, and in case the gases are high in olefin content, it has been found that the olens are preferentially absorbed by the oil. It is intended that about 5-20%, and preferably about 10%, of the gaseous hydrocarbons may be absorbed. r-lhe conditions maintained in the absorber Il] may be about the same as those maintained in the stabilizer 5.

The oil containing the absorbed gaseous hydrocarbons is Withdrawn from the bottom of the absorber through the line I8 and forced by the pump i9 to the cracking coil I6 located in a furnace 2l). In the cracking coil I6 a mixture of oil and absorbed gases is subjected to rather drastic conditions of temperature and pressure. These conditions may be about 500-1000 pounds pressure and about 9001050 F., preferably around 950- 1000" F. The cracked products are transferred from'heating coil I6 through the line 2| to a reaction chamber 22. A large proportion of the materials is vaporized, that proportion unvaporized dropping through the reaction chamber and continuously withdrawn thro-ugh the draw-off line 24 at the bottom of the chamber. Vapors and gases pass through the vapor line 25 to a fractionator 26. In the latter fractionator substantially all the products of higher boiling point than gasoline are fractionated and condensed out, the uncondensed gases passing overhead through the vapor line 28 and condenser 29 to an accumulator 3U. The reflux condensate or recycle stock condensing out in fractionator 26 is drawn through a line 32 and recycled by the pump 33 to the heating coil I6. In some cases, particularly When the gaseous charge is high in olefin content, it is desirable to use all or a. portion of this recycle stock as a scrubbing medium, and for this purpose, the recycle stock may be passed through the branch line 34 toI the upper portion of the absorber I0. 'I'his recycle stock is often effective for selectively extracting the olefins from the gas. The product collecting in the accumulator 30 is a gasoline usually of high antiknock quality. This product may be withdrawn from the accumulator through th'e draw-off line 36 While the uncondensed gaseous hydrocarbons may be released from the top of the accumulator through the line 31.

The gaseous hydrocarbons unabsorbed by the oil in the absorber l are withdrawn from the upper portion of the absorber through the line 40 and forced by pump 4| to a polymerization coil 42, located in a furnace 44. These gases are usually relatively high in paraflin content and are suitable for thermal polymerization. The polymerizing conditions maintained in coil 42 are the conventional conditions used for thermal polymerization, such as pressures from 50G-5000 pounds and temperatures of 900-1100 F., and preferably pressures of around 1000-2500 pounds and temperatures of about 1020-1070 F. The polymerization products are transferred through the line 45 in which may be located a transfer line heat exchanger or other cooling means, to a fractionator 46. In this fractionator the high boiling hydrocarbons, such as tars, are condensed and Withdrawn from the bottom thereof through the line 48. The uncondensed vapors and gases are conducted from the top of the fractionator 46 through the line 49 to a secondary fractionator 50. In the fractionator 50 the normally liquid hydrocarbons usually of gasoline boiling range, are condensed and fractionated out and withdrawn from the bottom thereof, through the line The intermediate boiling point fraction containing a large proportion of C3 and C4 hydrocarbons may be withdrawn from an intermediate point in the fractionator 50 through the line 53 and recycled by the pump 54 to the polymerization coil. The unpolymerized gases are Withdrawn from the top of the fractionator 50 and these gases together with those Withdrawn from the top of the accumulator 30 may be returned through the line 56 in which is located pump 51, to the stabilizer 5 to be retreated in the system.

As an example of the operation of the invention, cracking still gases containing about :zO-30% unsaturated constituents were scrubbed with recycle stock from a cracking system, operating on a recycle basis. Charge rates were maintained so that approximately of the gases was absorbed. The mixture of oil and absorbed gases was charged to a cracking coil wherein cracking conditions of about '750 pounds and about 975 F. were maintained. About 6-'7% increase in yield of gasoline was obtained in the cracking operation over that which would normally be obtained Without the presence of the absorbed gases. The gasoline also had an increased antiknock value of 2 or 3 points and a better grade of fuel oil and less coke were produced. The scrubbed gases are subjected to thermal polymerization at 2000 pounds pressure and about 1050 F., and a time of reaction of about 40 seconds. In addition, about 50-60% of the scrubbed gases is converted into liquid products in the polymerization operation.

Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made Without Ideparting from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

l. A process for the conversion oi.' hydrocarbon oils and gases into gasoline, which comprises subjecting a fresh charging stock consisting essentially of normally gaseous hydrocarbons of the class of natural and refinery gases to stabilization to separate therefrom fixed gases lighter than C3 hydrocarbons, scrubbing the remaining gases with a hydrocarbon oil cracking stock to absorb a portion of the higher boiling saturated and unsaturated constituents, subjecting unabsorbed gases to a separate polymerization operation in the absence of combustion gases at temperatures and pressures sufcient to form a maximum amount of aliphatic polymers boiling within the gasoline boiling point range, separating said polymers from unpolymerized gases, subjecting the mixture of cracking stock and absorbed gases to a separate conversion operation at temperatures suflicient to effect conversion 'thereof into gasoline, separating a gasoline fraction and a residual gaseous fraction from the cracked products, and recycling said residual gaseous fraction from the cracking operation and said unpolymerized gases from the polymerization operation to said stabilization operation.

2. A process for the conversion of hydrocarbon oils and gases into gasoline, which cornprises subjecting a fresh charging stock, consisting essentially of normally gaseous hydrocarbons of the class of natural and refinery gases, to a stabilizing operation by substantially removing therefrom the xed gases lighter than C3 hydrocarbons, then subjecting the remaining gases to an absorption operation by contacting therewith a hydrocarbon oil cracking stock whereby a portion of higher boiling saturated and unsaturated constituents of the gases is absorbed by said cracking stock, `subjecting the unabsorbed gases from. the absorption operation to a separate polymerizing operation in the absence of combustion gases under pressures of about 500 to 5000 pounds and temperatures of about 900 to 1100 F. whereby normally liquid hydrocarbons essentially of aliphatic character are formed, separating said normally liquid hydrocarbons from unpolymerized gases, subjecting the mixture of cracking stock and absorbed gases to a separate conversion operation at temperatures sufficient to effect conversion of the cracking stock and gases into gasoline, separating gasoline and residual gases from the cracked products and recycling said residual gases from the cracking operation and said unpolymerized gases from the polymerization operation to said stabilizing operation.

WAYNE E. KUHN. 

